[BS en ISO 14644-12] -- Cleanrooms and Associated Controlled Environments. Part 12. Classification of Air Cleanliness by Nanoscale Particle Concentration

Draft for Public Comment

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Title:

Draft BS ENISO 14644-12 Cleanrooms and associated controlled environments Part 12: Classification of air cleanliness by nanoscale particle concentration

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DRAFT INTERNATIONAL STANDARD ISO/DIS 14644-12 ISO/TC 209

Secretariat: ANSI

Voting begins on 2013-04-04

Voting terminates on 2013-09-04

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION

•

МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ

•

ORGANISATION INTERNATIONALE DE NORMALISATION

Cleanrooms and associated controlled environments — Part 12: Classification of air cleanliness by nanoscale particle concentration Salles propres et environnements maîtrisés apparentés — Partie 12: Classification de la propreté de l'air en fonction de la concentration des nanoparticules

ICS 13.040.35

ISO/CEN PARALLEL PROCESSING This draft has been developed within the International Organization for Standardization (ISO), and processed under the ISO-lead mode of collaboration as defined in the Vienna Agreement. This draft is hereby submitted to the ISO member bodies and to the CEN member bodies for a parallel five-month enquiry. Should this draft be accepted, a final draft, established on the basis of comments received, will be submitted to a parallel two-month approval vote in ISO and formal vote in CEN.

To expedite distribution, this document is circulated as received from the committee secretariat. ISO Central Secretariat work of editing and text composition will be undertaken at publication stage. Pour accélérer la distribution, le présent document est distribué tel qu'il est parvenu du secrétariat du comité. Le travail de rédaction et de composition de texte sera effectué au Secrétariat central de l'ISO au stade de publication.

THIS DOCUMENT IS A DRAFT CIRCULATED FOR COMMENT AND APPROVAL. IT IS THEREFORE SUBJECT TO CHANGE AND MAY NOT BE REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHED AS SUCH. IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT INTERNATIONAL STANDARDS MAY ON OCCASION HAVE TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME STANDARDS TO WHICH REFERENCE MAY BE MADE IN NATIONAL REGULATIONS. RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT, WITH THEIR COMMENTS, NOTIFICATION OF ANY RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE AND TO PROVIDE SUPPORTING DOCUMENTATION.

© International Organization for Standardization, 2013

ISO/DIS 14644-12

COPYRIGHT PROTECTED DOCUMENT © ISO 2013 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of the requester. ISO copyright office Case postale 56 • CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail [email protected] Web www.iso.org Published in Switzerland

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ISO/DIS 14644-12

Contents

Page

Foreword ............................................................................................................................................................ iv Introduction ......................................................................................................................................................... v 1

Scope ...................................................................................................................................................... 1

2

Normative references ............................................................................................................................ 1

3 3.1 3.2 3.3 3.4 3.5

Definitions .............................................................................................................................................. 2 General ................................................................................................................................................... 2 Size.......................................................................................................................................................... 2 Airborne particles .................................................................................................................................. 3 Occupancy states .................................................................................................................................. 3 Measuring apparatus ............................................................................................................................ 4

4 4.1 4.2 4.3 4.4

Classification ......................................................................................................................................... 4 General ................................................................................................................................................... 4 Occupancy states .................................................................................................................................. 4 Classification number ........................................................................................................................... 5 Designation ............................................................................................................................................ 6

5 5.1 5.2 5.3

Demonstration of compliance .............................................................................................................. 6 Principle.................................................................................................................................................. 6 Testing .................................................................................................................................................... 6 Airborne concentration ......................................................................................................................... 7

6

Test report .............................................................................................................................................. 7

Annex A (normative) Reference method for determination of ACP classification by condensation particle counting .................................................................................................................................... 8 A.1 Principle.................................................................................................................................................. 8 A.2 Apparatus requirements ....................................................................................................................... 8 A.3 Particle counting efficiency and particle size cut-off ........................................................................ 9 A.4 Pretest conditions ................................................................................................................................. 9 A.5 Sampling................................................................................................................................................. 9 A.6 Recording of results ............................................................................................................................ 10 A.7 Interpretation of results - Classification requirements ................................................................... 11 A.8 Test reports .......................................................................................................................................... 11 Annex B (informative) Particle counting efficiency and particle size cutoff ............................................... 12 B.1 Counting efficiency ............................................................................................................................. 12 B.2 Particle size cutoff device................................................................................................................... 13 B.3 Nanoscale particle size distribution .................................................................................................. 14 Annex C (informative) Overview of particle size characteristics ................................................................. 15 C.1 Introduction .......................................................................................................................................... 15 C.2 Differences between large and small particles ................................................................................ 15 C.3 Cleanrooms .......................................................................................................................................... 16 Bibliography ...................................................................................................................................................... 18

© ISO 2012 – All rights reserved

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Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 14644-12 was prepared by Technical Committee ISO/TC 209, Cleanrooms and associated controlled environments. ISO 14644 consists of the following parts, under the general title Cleanrooms and associated controlled environments: 

Part 1: Classification of air cleanliness



Part 2: Specifications for testing and monitoring to prove continued compliance with ISO 14644-1



Part 3: Test methods



Part 4: Design, construction and start-up



Part 5: Operations



Part 6: Vocabulary



Part 7: Separative devices (clean air hoods, gloveboxes, isolators, and mini-environments)



Part 8: Classification of airborne molecular contamination



Part 9: Classification of surface cleanliness by particle concentration



Part 10: Classification of surface cleanliness by chemical concentration



Part 12: Classification of air cleanliness by nanoscale particle concentration

Attention is also drawn Biocontamination control:

to

ISO 14698,

Cleanrooms

and



Part 1: General principles and methods



Part 2: Evaluation and interpretation of biocontamination data

iv

associated

controlled

environments —

© ISO 2012 – All rights reserved

ISO/DIS 14644-12

Introduction Cleanrooms and associated controlled environments provide the control of contamination to levels appropriate for accomplishing contamination-sensitive activities. Products and processes that benefit from the control of contamination include those in such industries as aerospace, microelectronics, pharmaceuticals, medical devices, healthcare and food. ISO Technical Committee 209 Cleanrooms and associated controlled environments has issued standards ISO 14644-1 and ISO 14644-3 as listed in the Foreword. The normative requirements in these standards were limited to classification of particles greater than 100 nm. However, informative material was included in both documents for airborne particles smaller than 100 nm. At the time these documents were written, particles smaller than 100 nm were called ultrafine particles rather than the more recent term, nanoparticles. In the course of current Revisions, sections on ultrafine particles have been removed from ISO 14644 Parts 1 and 3 and incorporated, in modified form, in the present document ISO 14644-12. ISO 14644-12 also extends the airborne particle classification scheme in ISO 14644-1 to particle sizes smaller than 100 nm. Supporting information has also been drawn from documents developed elsewhere, e.g. by ISO Technical Committee 229 Nanotechnologies. Nanotechnology is a recently organized field, typically dealing with material in the size range of approximately 1 nm to 100 nm. As part of the long term trend of manufacturing products with ever smaller feature size to improve performance, many industries such as microelectrics and those related to health now have products in the nanoscale. See Annex C for background information on particle size characteristics/properties. NOTE In consideration of some similarities of rationale and structure between ISO 14644-12 and ISO 14644-1, it is conceivable that these two parts of ISO 14644 could be merged in the future. However, this is not envisaged at present.

© ISO 2012 – All rights reserved

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DRAFT INTERNATIONAL STANDARD

ISO/DIS 14644-12

Cleanrooms and associated controlled environments — Part 12: Classification of air cleanliness by nanoscale particle concentration

Caution It is to be noted that the customary classification of cleanrooms by particle concentration requires the use of ISO 14644-1. Nanoscale particle classification using 14644-12 should under operational conditions only be used in addition to particle classification using 14644-1.

1

Scope

This part of ISO 14644 covers the classification of air cleanliness by particles (ACP) in terms of concentration of airborne nanoscale particles. For classification purposes, only populations of particles with a lower size limit of 0.1 microns (100 nm) or less - "nanoscale" - are considered. The classification given in this document is for use mainly in "in operation" states. This classification extrapolates the particulate classification equation specified in 14644-1 into the nanoscale (< 100 nm) region. NOTE 1 For the purposes of this document, reference will be made to "nanoscale particles", which here signify all nano-objects having one (nanoplate), two (nanofibre) or three (nanoparticle) dimensions in the nanoscale. NOTE 2 It should be noted that the actual behaviour of particles in the cleanroom depends on their sources and physical behaviour. NOTE 3

2

Health and safety considerations are excluded from this document.

Normative references

ISO 14644-1:1999 Cleanrooms and associated controlled environments -- Part 1: Classification of air cleanliness by particle concentration ISO 14644-3:2005 Cleanrooms and associated controlled environments -- Part 3: Test methods ISO 15900:2009 Determination of particle size distribution -- Differential electrical mobility analysis for aerosol particles ISO 21501-4:2007 Determination of particle size distribution -- Single particle light interaction methods -- Part 4: Light scattering airborne particle counter for clean spaces ISO/TS 27687:2008 Nanotechnologies -- Terminology and definitions for nano-objects -- Nanoparticle, nanofibre and nanoplate 1

1 ISO/TS 80004-2, in preparation, will supersede ISO/TS 27687.

© ISO 2012 – All rights reserved

1

ISO/DIS 14644-12

ISO 27891 2 Aerosol particle number concentration -- Calibration of condensation particle number counters ISO/TS 80004-1:2010 Nanotechnologies -- Vocabulary -- Part 1: Core terms

3

Definitions

For the purposes of this part of ISO 14644, the definitions given in ISO 14644-1, ISO 14644-3, ISO/TS 27687 and ISO/TS 80004-1 and the following apply.

3.1

General

3.1.1 cleanroom room in which the concentration of airborne particles is controlled, and which is constructed and used in a manner to minimize the introduction, generation, and retention of particles inside the room, and in which other relevant parameters, e.g. temperature, humidity, and pressure, are controlled as necessary [ISO 14644-1: definition 2.1.1] 3.1.2 clean zone dedicated space in which the concentration of airborne particles is controlled, and which is constructed and used in a manner to minimize the introduction, generation, and retention of particles inside the zone and in which other relevant parameters, e.g. temperature, humidity, and pressure, are controlled as necessary NOTE

This zone may be open or enclosed and may or may not be located within a cleanroom.

[ISO 14644-1: definition 2.1.2]

3.2

Size

3.2.1 nanoscale size range from approximately 1 nm to 100 nm NOTE 1 Properties that are not extrapolations from a larger size will typically, but not exclusively, be exhibited in this size range. For such properties the size limits are considered approximate. NOTE 2 The lower limit in this definition (approximately 1 nm) is introduced to avoid single and small groups of atoms from being designated as nano-objects or elements of nanostructures, which might be implied by the absence of a lower limit.

[ISO 27687: definition 2.1] 3.2.2 nano-object material with one, two or three external dimensions in the nanoscale NOTE

Generic term for all discrete nanoscale objects.

[ISO 27687: definition 2.2]

2 To be published .

2

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ISO/DIS 14644-12

3.2.3 particle size cutoff D50 particle size at which the counting efficiency is 50 % NOTE

3.3

See annex B for explanation of counting efficiency.

Airborne particles

3.3.1 nanoparticle nano-object with all three external dimensions in the nanoscale NOTE If the lengths of the longest to the shortest axes of the nano-object differ significantly (typically by more than three times), the terms nanorod or nanoplate are intended to be used instead of the term nanoparticle.

[ISO 27687: definition 4.1] 3.3.2 particle size distribution cumulative distribution of particle concentration as a function of particle size [ISO 14644-1: definition 3.2.4] 3.3.3 aerosol system of solid or liquid particles suspended in gas [ISO 15900: definition 2.1]

3.4

Occupancy states

3.4.1 as built condition where the cleanroom or clean zone is complete with all services connected and functioning but with no production equipment, materials, or personnel present [14644-1: definition 2.4.1] 3.4.2 at-rest condition where the cleanroom or clean zone is complete with equipment installed and operating in a manner agreed upon by the customer and supplier, but with no personnel present [14644-1: definition 1.4.2] 3.4.3 operational condition where the cleanroom or clean zone is functioning in the specified manner, with the specified number of personnel present and working in the manner agreed upon [14644-1: definition 2.4.3]

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ISO/DIS 14644-12

3.5

Measuring apparatus

3.5.1 condensation particle counter CPC instrument that measures the airborne particle number concentration by condensing a liquid onto the particles from a supersaturated vapour and counting the resulting droplets NOTE 1 The sizes of particles detected are usually smaller than several hundred nanometres and larger than a few nanometres. NOTE 2

A CPC is one possible detector for use with a differential electrical mobility analyser.

NOTE 3

In some cases, a condensation particle counter may be called a condensation nucleus counter (CNC).

3.5.2 differential electrical mobility classifier DEMC classifier that is able to select aerosol particles according to their electrical mobility and pass them to its exit NOTE A DEMC classifies aerosol particles by balancing the electrical force on each particle with its aerodynamic drag force in an electrical field. Classified particles are in a narrow range of electrical mobility determined by the operating conditions and physical dimensions of the DEMC, while they can have different sizes due to differences in the number of charges that they have

[ISO 15900: definition 2.7] 3.5.3 differential mobility analyzing system DMAS system to measure the size distribution of submicrometre aerosol particles consisting of a DEMC, flow meters, a particle detector, interconnecting plumbing, a computer and suitable software [ISO 15900: definition 2.8] 3.5.4 Counting efficiency ratio of the reported concentration of particles in a given size range to the actual concentration of such particles [ISO 14644-3: definition 3.6.5]

4 4.1

Classification General

For the purposes of this classification document the term "nanoscale particles" will be used instead of the generic term "nano-objects". This is necessary because, for measurement purposes, the only important particle characteristic is its "equivalent diameter". In this document, "nanoscale particle" signifies any object with one, two or three dimensions in the nanoscale.

4.2

Occupancy states

The nanoscale particle cleanliness of air in a cleanroom or clean zone shall be defined in one or more of three occupancy states: “as-built”, “at-rest”, or “operational” (see 3.4).

4

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ISO/DIS 14644-12

4.3

Classification number

The air particle cleanliness class in a cleanroom or associated controlled environment shall be designated by a classification number, N, specifying the maximum total particle concentration in air permitted for a considered nanoscale particle size. NOTE This is an extension of the considered particle size range of the classification described in 14644-1 into the nanoscale.

Airborne particulate cleanliness shall be designated by a classification number, N. The maximum permitted concentration of particles Cn, for each considered particle size, D, is determined by the formula [ISO 4644-1]: N

Cn,m =10 x (0.1/D)

2.08

(1)

where: 3

Cn,m represents the maximum permitted concentration (in particles/m ) of airborne particles at a specific class that are equal to or larger than the considered particle size. Cn,m is rounded to the nearest whole number, using no more than three significant figures. N

is the ISO classification number, which shall not exceed a value of 9.

D

is the considered particle size in μm.

0,1 is a constant with a dimension of μm. NOTE 1 Equation 1 was used to compute particle concentrations expected for classifications of particles smaller than 0,1 μm extending the classes in ISO 14644-1. It is acknowledged that metrology may not be available at the present time to quantify all the presented classes. NOTE 2 A given facility may have a classification for microscale cleanliness under ISO 14644-1 and nanoscale cleanliness under ISO 14644-12. NOTE 3

The cleanroom is tested in an operational state – see C.3.

The maximum permitted concentration of particles, Cn,m, for each considered particle size, D, is determined from Table 1. Table 1 – Classification table for ISO-ACP classes

Classification

Particle sizes 0,001µm

(1nm)d

0,005µm (5nm)

0,01µm (10nm)

0,05µm (50nm)

0,1 µm

1

145 000 d

5 080

1 200

c

2

1 450 000 d

50 800

12 000

423

100

3

14 500 000 d

508 000

120 000

4 230

1 000

4

145 000 000d

5 080 000

1 200 000

42 300

10 000

5

b

50 800 000

12 000 000

423 000

100 000

6

b

b

b

4 230 000

1 000 000

7

b

b

b

b

b

8

b

b

b

b

b

9

b

b

b

b

b

10

a

Notes:

© ISO 2012 – All rights reserved

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ISO/DIS 14644-12

1 2 a) b) c) d)

4.4

The 0,01µm particle size from ISO 14644-1 is included for reference. Attention is drawn to the Caution given on page 1. All concentrations in the table are cumulative. e.g. for ISO-ACP Class 3, the 120 000 particles shown at 10 nm include all particles equal to and greater than this size, These concentrations will lead to large air sample volumes for classification. See Annex D [ISO 14644-1] Sequential sampling. Concentration limits are not applicable in this region of the table due to very high particle concentration. Sampling and statistical limitations for particles in low concentrations make classification inappropriate. At the time of publication, counting at this particle size is beyond current instrumentation. This column has been added for future application.

Designation

The designation of nanoscale air particle cleanliness class for cleanrooms and clean zones shall include: a) the classification number, expressed as “ISO-ACP Class N ”; b) the occupancy state to which the classification applies; c) the considered particle size(s), and the related class limit(s), as determined by the classification table (Table1) or equation (1) where each considered threshold particle size is in the range from 0,05 μm to 0,001 μm. The considered particle size(s) for which the concentration(s) will be measured shall be agreed upon by the customer and the supplier. EXAMPLE

Nanoscale particle classification

Applying 14644-12, a condensation particle counter measurement in operation of 1000 counts at size ≥ 10 nm would lead to the following ISO-ACP classification: ISO-ACP Class 1; in operation;10 nm

5 5.1

Demonstration of compliance Principle

Compliance with air cleanliness (ISO ACP class) requirements specified by the customer is verified by performing specified testing procedures and by providing documentation of the results and conditions of testing, as agreed upon by the customer and the supplier.

5.2

Testing

For the purposes of ACP classification, airborne nanoscale particle counting can be carried out most effectively by CPC. The reference test method for ACP classification by CPC is given in annex A. Criteria for determining the counting method shall include: - nanoscale particle size to be measured ; - time dependence of sampling and analysis; - sample volume;

6

© ISO 2012 – All rights reserved

ISO/DIS 14644-12

- location of sampling; - number of samples; - criticality of process/product; - design/layout of clean zone. Alternative methods and/or instrumentation, having at least comparable performance to CPC measurement, may be specified. If no alternative is specified or agreed upon, the reference method shall be used. Tests performed to demonstrate compliance shall be conducted using calibrated instruments.

5.3

Airborne concentration

Upon completion of testing in accordance with 5.2, the concentration of particles (expressed as number of particles per m3) in the sample volume tested shall not exceed the concentration limit(s) given in Table 1 or derived from equation (1) for intermediate classes for the considered size(s). If multiple single sample volumes are taken at a sample location, the concentration shall be averaged and the average concentration shall not exceed the concentration limits given in Table 1 or derived from equation (1) for intermediate classes. Particle concentrations used for determination of conformity with classification limits shall be measured by the same method for all considered particle sizes.

6

Test report

The results from testing each clean zone shall be recorded and submitted as a comprehensive report, along with a statement of compliance or non-compliance with the specified designation of ACP classification. The test report shall include: a) the name and address of the testing organization, and the date on which the test was performed; b) the number and year of publication of this part of ISO 14644, i.e. ISO 14644-12: date of current issue; c) a clear identification of the physical location of the clean zone tested (including reference to adjacent areas if necessary), and specific designations for coordinates of all sampling locations; d) the specified designation criteria for the clean zone, including the ISO ACP classification, the relevant occupancy state(s), and the considered particle size(s); e) details of the test method used, with any special conditions relating to the test, or departures from the test method, and identification of the test instrument and its current calibration certificate; f) the test results, including particle concentration data for all sampling locations.

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ISO/DIS 14644-12

Annex A (normative) Reference method for determination of ACP classification by condensation particle counting

A.1 Principle A CPC instrument is used to determine the concentration of airborne nanoscale particles, equal to and greater than the specified sizes, at designated sampling locations.

A.2 Apparatus requirements A.2.1 CPC instrument The instrument shall have a means of displaying or recording the count of airborne nanoscale particles in air with a size discrimination capability to detect the total nanoscale particle concentration in the appropriate particle size ranges for the class under consideration.

A.2.2 Condensation particle counter (CPC) The instrument counts all droplets formed by condensation of supersaturated vapour on sampled nuclei particles. Cumulative particle concentrations are produced for particles larger than or equal to the lower size limit of the CPC. The specifications for the condensation particle counter are given in Table A.1. Table A.1 — Specifications for condensation particle counter

8

Item

Specification

Upper concentration limit

>3,5 x 109/m3

Particle size cutoff (D50)

Application specific, e.g. D50 = 0,01 µm (see table 1)

Accuracy of count measurement

+/- 10 % at below the upper concentration limit

Ambient conditions for stability of reading

Temp. range: 10 ˚C– 35 ˚C Relative Hum.: 0 – 90 % non-condensing Ambient pressure: 75 kPa – 105 kPa (0.75 atm – 1.1 atm.)

Flow rate stability

+/- 10% of specified flow at T/RH/P that tests will be conducted

Calibration interval

12 months maximum

False count error

False counts shall be less than a 1/3 of the maximum permitted concentration in Table 1, (see following example)

Counting efficiency

50% +/- 10% at the lower size limit, and >85% at 5x the lower size limit, and